Study of the Diffusion Behavior of Seawater Absorption in Multi-Walled Carbon Nanotubes/Halloysite Nanotubes Hybrid Nanofillers Modified Epoxy-Based Glass/Carbon Fiber Composites

In the maritime industry, cost-effective and lightweight Fiber Reinforced Polymer (FRP) composites offer excellent mechanical properties, design flexibility, and corrosion resistance. However, their reliability in harsh seawater conditions is a concern. Researchers address this by exploring three approaches: coating fiber surfaces, hybridizing fibers and matrices with or without nanofillers, and interply rearrangement. This study focuses on evaluating the synergistic effects of interply rearrangement of glass/carbon fibers and hybrid nanofillers, specifically Multi-walled carbon nanotubes (MWCNT) and Halloysite nanotubes (HNT). The aim is to enhance impact properties by minimizing moisture absorption. Hybrid nanocomposites with equal-weight proportions of two nanofillers: 0 wt.%, 1 wt.%, and 2 wt.% were exposed to seawater for 90 days. Experimental data was subjected to modelling through the application of Predictive Fick’s Law. The study found that the hybrid composite containing 2 wt.% hybrid nanofillers exhibited a 22.10% increase in impact performance compared to non-modified counterparts. After 90 days of seawater aging, the material exhibited enhanced resistance to moisture absorption (15.74%) and minimal reduction in impact strength (8.52%) compared to its dry strength, with lower diffusion coefficients.

Abnormal magnetic behavior of prussian blue analogs modified with multi-walled carbon nanotubes

This work examines the origin of the abnormal magnetism exhibited by Cu Mn Fe-PBAs modified with multi-walled carbon nanotubes(MWCNTs).The system of Cu Mn Fe-PBAs@MWCNTs coexists with both large and small clusters.Cu Mn Fe-PBAs clusters have an average particle size of 28 nm,and some of the smaller particles are adsorbed on the surface of MWCNTs.Surprisingly,the magnitude of magnetization increases linearly with decreasing temperature.When above the Curie temperature,the magnitude of magnetization is significantly greater than that of PBAs without being modified.This phenomenon can be attributed to magnetostatic interactions between ultra-fine magnetic nanoparticles adsorbed on the surface of MWCNTs.Using the Monte Carlo method,we simulated the magnetostatic interaction of cylindrical adsorbed particles,and the simulation results are almost identical to those observed experimentally.The results indicate that 0.089Cu Mn Fe-PBAs clusters per 1 nm^(2)can be adsorbed onto the surface area of MWCNTs.We demonstrate that MWCNTs adsorbing magnetic particles exhibit magnetic behavior,and suggest a method for producing ultrafine materials.It also introduces a new method of calculating the adsorption efficiency of carbon nanotubes,offering theoretical guidance for future research on nanomaterials with enhanced adsorption efficiency.

Toxicity of Multi-Walled Carbon Nanotubes,Graphene Oxide,and Reduced Graphene Oxide to Zebrafish Embryos

Objective This study was aimed to investigate the toxic effects of 3 nanomaterials, i.e. multi-walled carbon nanotubes （MWCNTs）, graphene oxide （GO）, and reduced graphene oxide （RGO）, on zebrafish embryos. Methods The 2-h post-fertilization （hpf） zebrafish embryos were exposed to MWCNTs, GO, and RGO at different concentrations （1, 5, 10, 50, 100 mg/L） for 96 h. Afterwards, the effects of the 3 nanomateria on spontaneous movement, heart rate, hatching rate, length of larvae, mortality, and malformations Is were evaluated. Results Statistical analysis indicated that RGO significantly inhibited the hatching of zebrafish embryos. Furthermore, RGO and MWCNTs decreased the length of the hatched larvae at 96 hpf. No obvious morphological malformation or mortality was observed in the zebrafish embryos after exposure to the three nanomaterials. Conclusion MWCNTs, GO, and RGO were all toxic to zebrafish embryos to influence embryos hatching and larvae length. Although no obvious morphological malformation and mortality were observed in exposed zebrafish embryos, further studies on the toxicity of the three nanomaterials are still needed.

Ultrasensitive electrochemical determination of metronidazole based on polydopamine/carboxylic multi-walled carbon nanotubes nanocomposites modified GCE

An ultrasensitive electrochemical sensor based on polydopamine/carboxylic multi-walled carbon nanotubes(MWCNTs à COOH) nanocomposites modified glassy carbon electrode(GCE) was presented in this work, which has been developed for highly selective and highly sensitive determination of an antimicrobial drug, metronidazole. The preparation of polydopamine/MWCNTs–COOH nanocomposites/GCE sensor is simple and possesses high reproducible, where polydopamine can be coated on the surface of MWCNTs–COOH via a simple electropolymerization process. Under optimized conditions, the proposed sensor showed ultrasensitive determination for metronidazole with a wide linear detection range from5 to 5000 mmol/dm^3 and a low detection limit of 0.25 mmol/dm^3(S/N=3). Moreover, the proposed sensor has been successfully applied for the quantitative determination of metronidazole in real drug samples. This work may provide a novel and effective analytical platform for determination of metronidazole in application of real pharmaceutical and biological samples analysis.

In situ synthesis of palladium nanoparticles on multi-walled carbon nanotubes and their electroactivity for ethanol oxidation

Pd nanoparticles(Pd-NPs)were prepared and directly anchored on the surface of multi-walled carbon nanotubes(MWCNTs)in the absence of chemical reduction agent,where MWCNTs were used as both the chemical reduction agent and the support substrate of Pd-NPs.Effect of various surfactants on the in situ deposition of PdNPs on MWCNTs was investigated.When MWCNTs were modified with a cationic surfactant(hexadecyl trimethyl ammonium bromide,CTAB),the amount of the Pd-NPs(Pd-NP/CTAB-MWCNT)generated by such an in situ deposition method gets a notable increase,and the size of the as-synthesized Pd-NPs becomes smaller,compared with those in the absence of any surfactant(Pd-NP/MWCNT)or in the presence of an anionic surfactant SDS(Pd-NP/SDS-MWCNT)and a neutral surfactant OP(PdNP/OP-MWCNT).Results show that the MWCNTs modified with CTAB are propitious to the in situ reduction of Pd2?.Among the prepared catalysts,Pd-NP/CTABMWCNT displays the highest electroactivity for ethanol oxidation in alkaline media.

Production of High Purity Multi-Walled Carbon Nanotubes from Catalytic Decomposition of Methane

Acid-based purification process of multi-walled carbon nanotubes （MWNTs） produced via catalytic decomposition of methane with NiO/TiO2 as a catalyst is described. By combining the oxidation in air and the acid refluxes, the impurities, such as amorphous carbon, carbon nanoparticles, and the NiO/TiO2 catalyst, are eliminated. Scanning electron microscopy （SEM） and transmission electron microscopy （TEM） images confirm the removal of the impurities. The percentage of the carbon nanotubes purity was analyzed using thermal gravimetric analysis （TGA）. Using this process, 99.9 wt% purity of MWNTs was obtained.

Adsorption and desorption phenomena on thermally annealed multi-walled carbon nanotubes by XANES study

The multi-walled carbon nanotubes(MWCNTs) studied in this work were synthesized by the catalytic chemical vapor deposition(CCVD) process, and were thermally annealed by the hot filament plasma enhanced(HF PE) method at 550℃ for two hours.The x-ray absorption near edge structure(XANES) technique was used to investigate the adsorption and desorption phenomena of the MWCNTs at normal and grazing incidence angles.The adsorbates were found to have different sensitivities to the thermal annealing.The geometry of the incident beam consistently gave information about the adsorption and desorption phenomena.In addition, the adsorption of non-intrinsic potassium quantitatively affected the intrinsic adsorbates and contributed to increase the conductivity of the MWCNTs.The desorption of potassium was almost 70% greater after the thermal annealing.The potassium non-intrinsic adsorbates are from a physisorption mechanism whereas the intrinsic adsorbates result from chemisorption.

FLEXURAL WAVE DISPERSION IN MULTI-WALLED CARBON NANOTUBES CONVEYING FLUIDS

Motivated by the great potential of carbon nanotubes for developing nanofluidic devices, this paper presents a nonlocal elastic, Timoshenko multi-beam model with the second order of strain gradient taken into consideration and derives the corresponding dispersion relation of flexural wave in multi-walled carbon nanotubes conveying fuids. The study shows that the moving flow reduces the phase velocity of flexural wave of the lowest branch in carbon nanotubes. The phase velocity of flexural wave of the lowest branch decreases with an increase of flow velocity. However, the effects of flow velocity on the other branches of the wave dispersion are not obvious. The effect of microstructure characterized by nonlocal elasticity on the dispersion of flexural wave becomes more and more remarkable with an increase in wave number.

Purified oxygenand nitrogen-modified multi-walled carbon nanotubes as metal-free catalysts for selective olefin hydrogenation

Oxygen and nitrogen-functionalized carbon nanotubes （OCNTs and NCNTs） were applied as metal-free catalysts in selective olefin hydro- genation. A series of NCNTs was synthesized by NH3 post-treatment of OCNTs. Temperature-programmed desorption, N2 physisorption, Raman spectroscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy were employed to characterize the surface properties of OCNTs and NCNTs, aiming at a detailed analysis of the type and amount of oxygen- and nitrogen-containing groups as well as surface defects. The gas-phase treatments applied for oxygen and nitrogen functionalization at elevated temperatures up to 600 ℃ led to the increase of surface defects, but did not cause structural damages in the bulk. NCNTs showed a clearly higher activity than the pristine CNTs and OCNTs in the hydrogenation of 1,5-cyclooctadiene, and also the selectivity to cyclooctene was higher. The favorable catalytic properties are ascribed to the nitrogen-containing surface functional groups as well as surface defects related to nitrogen species. In contrast, oxygen-containing surface groups and the surface defects caused by oxygen species did not show clear contribution to the hydrogenation catalysis.

Preconcentration of copper with multi-walled carbon nanotubes pretreated by potassium permanganate cartridge for solid phase extraction prior to flame atomic absorption spectrometry

A procedure for the preconcentration of copper was described in this paper using multi-walled carbon nanotubes (MWCNTs) oxidized by potassium permanganate as the adsorbent for the enrichment of trace copper in water samples. Important parameters, such as the sample pH, the concentration and volume of eluent, sample flow rate and volume, and interference of coexisting ions, were investigated. The obtained results indicated that proposed method possessed an excellent analytical performance. The linear range, the detection limit, and precison (RSD) were 1–100 ng/mL (R(2) = 0.9993), 0.32 ng/mL and 2.88%, respectively. The results showed that copper could be adsorbed quantitatively on the pretreated MWCNTs with potassium permanganate, and proposed method was very useful in the monitoring of copper in the environment.

Glassy carbon electrode modified with multi-walled carbon nanotubes sensor for the quantihication of antihistamine drug pheniramine in solubilized systems

A sensitive electroanalytical method for quantification of pheniramine in pharmaceutical formulation has been investigated on the basis of the enhanced electrochemical response at glassy carbon electrode modified with multi-walled carbon nanotubes in the presence of sodium lauryl sulfate.The experimental results suggest that the phcniramine in anionic surfactant solution exhibits electrocatalytic effect resulting in a marked enhancement of the peak current response.Peak current response is linearly dependent on the concentration of pheniramine in the range 200-1500 μg/mL with correlation coefficient 0.9987.The limit of detection is 58.31 μg/m L.The modified electrode shows good sensitivity and repeatability.

Synthesis and Characterization of W-doped TiO_2 Supported by Hybrid Carbon Nanomaterials of Multi-walled Carbon Nanotubes and C_(60) Fullerene by a Hydrothermal Method

W-doped TiO2 supported by hybrid carbon nanomaterials of multi-walled carbon nanotubes and C60 fullerene was synthesized by a simple hydrothermal method. The material displayed high visible light photocatalytic activity. X-ray diffraction, field emission transmission electron microscopy, ultra violet/visible light absorption and photoluminescence spectroscopy were used to characterize the material as photoeatalyst. Photocatalytic activity on the degradation of Rhodamine B dye in an aqueous solution under ultraviolet light and visible light irradiation was also studied. The experimental results indicated that the photocatalytic activity of the material was much higher than that of pure TiO2 or Degussa P25 TiO2.

Electrochemical Reduction of Oxygen on Multi-walled Carbon Nanotubes Electrode in Alkaline Solution

The multi-walled carbon nanotubes (MWNTs) electrode was constructed using poly-tetrafluoroethylene as binder, and the electrochemical reductive behavior of oxygen in alkaline solution was first examined on this electrode. Compared with other carbon materials, MWNTs show higher electrocatalytic activity, and the reversibility of O2 reduction reaction is greatly improved. The experiments reveal that the electrochemical reduction of O2 to HO2- is controlled by adsorption. The preliminary results illustrate the potential application of MWNTs in fuel cells.

Acetylcholinesterase Biosensor Based on Poly(diallyldimethylammonium chloride)-multi-walled Carbon Nanotubes-graphene Hybrid Film

In this paper, an amperometric acetylcholinesterase(ACh E) biosensor for quantitative determination of carbaryl was developed. Firstly, the poly(diallyldimethy-lammonium chloride)-multi-walled carbon nanotubes-graphene hybrid film was modified onto the glassy carbon electrode(GCE) surface, then ACh E was immobilized onto the modified GCE to fabricate the ACh E biosensor. The morphologies and electrochemistry properties of the prepared ACh E biosensor were investigated by using scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. All variables involved in the preparation process and analytical performance of the biosensor were optimized. Based on the inhibition of pesticides on the ACh E activity, using carbaryl as model compounds, the biosensor exhibited low detection limit, good reproducibility and high stability in a wide range. Moreover, the biosensor can also be used for direct analysis of practical samples, which would provide a new promising tool for pesticide residues analysis.

A comparative study of polymer nanocomposites containing multi-walled carbon nanotubes and graphene nanoplatelets

Featuring exceptional mechanical and functional performance, MWCNTs and graphene(nano)platelets(GNPs or Gn Ps;each platelet below 10 nm in thickness) have been increasingly used for the development of polymer nanocomposites. Since MWCNTs are now cost-effective at US$30 per kg for industrial applications, this work starts by briefly reviewing the disentanglement and surface modification of MWCNTs as well as the properties of the resulting polymer nanocomposites. GNPs can be made through the thermal treatment of graphite intercalation compounds followed by ultrasonication;GNPs would have lower cost yet higher electrical conductivity over 1,400 S cmthan MWCNTs. Through proper surface modification and compounding techniques, both types of fillers can reinforce or toughen polymers and simultaneously add anti-static performance. A high ratio of MWCNTs to GNPs would increase the synergy for polymers. Green, solvent-free systhesis methods are desired for polymer nanocomposites. Perspectives on the limitations, current challenges and future prospects are provided.

Prediction of Henry Constants and Adsorption Mechanism of Volatile Organic Compounds on Multi-Walled Carbon Nanotubes by Using Support Vector Regression

Support vector regression （SVR） combined with particle swarm optimization for its parameter optimization is employed to establish a model for predicting the Henry constants of multi-walled carbon nanotubes （MWNTs） for adsorption of volatile organic compounds （VOCs）. The prediction performance of SVR is compared with those of the model of theoretical linear salvation energy relationship （TLSER）. By using leave-one-out cross validation of SVR test Henry constants for adsorption of 35 VOCs on MWNTs, the root mean square error is 0.080, the mean absolute percentage error is only 1.19~, and the correlation coefficient （R2） is as high as 0.997. Compared with the results of the TLSER model, it is shown that the estimated errors by SVR are ali smaller than those achieved by TLSER. It reveals that the generalization ability of SVR is superior to that of the TLSER model Meanwhile, multifactor analysis is adopted for investigation of the influences of each molecular structure descriptor on the Henry constants. According to the TLSER model, the adsorption mechanism of adsorption of carbon nanotubes of VOCs is mainly a result of van der Waals and interactions of hydrogen bonds. These can provide the theoretical support for the application of carbon nanotube adsorption of VOCs and can make up for the lack of experimental data.

Preparation and Surface Modification of High-Density Chitosan/Functionalized Multi-walled Carbon Nanotubes Hollow Fibers

Functionalized multi-walled carbon nanotubes( fMWNTs) were prepared with chitosan via controlled surface deposition and crosslinking process and scanning electron microscopy( SEM),Fourier translation infrared spectroscopy( FT-IR) and Xray diffraction( XRD) are used to character properties. A novel high-density chitosan( HCS) was dissolved in f-MWNTs dispersed dilute acetic acid with a maximal concentration of 5. 8%. The hollow fibers can be made by extruding the solution into a dilute alkali solution through a wet-spinning process and the tensile properties of the materials were evaluated by universal tester. The surface property of fibers,pretreated by Helium( He) and the following grafted with gelatin was evaluated with X-ray photoelectron spectroscopy( XPS).As the hollow fibers were intended for neural tissue engineering,its suitability was evaluated in vitro using rat Schwann cells( RSC96) as model cells. The cells attachment,proliferation and morphology,were studied by various microscopic techniques. Based on the results,the gelatin grafted HCS / f-MWNTs hollow fibers could be used as a potential cell carrier in neural tissue engineering.

Ultra Sensitive Determination and Preconcentration of Cd²⁺, Cu²⁺and Pb²⁺after Multi-Walled Carbon Nanotubes Adsorption

Multi-Walled carbon nanotubes are used as preconcentrating probes for the quantitative determination of trace cadmium, copper and lead in environmental and biological sample using graphite Furnace Atomic Absorption Spectrometry and inductively coupled Plasma Optical Emission spectrometry. The method is based on the electrostatic interactions of positively charged Cd+, Cu+ and Pb+ with the negatively charged multi-walled carbon nanotubes (MWCNTs) for the preconcentration and isolation of analytes from sample solutions. Effective preconcentration of trace cadmium, copper and lead was achieved in a pH range of 5 - 7, 5 - 7 and 4 - 7, respectively. The retained cadmium, copper and lead were efficiently eluted with 0.3 mol·L-1 HCl for graphite Furnace Atomic Absorption Spectrometry determination. The multi-walled carbon nanotubes packed micro-column exhibited fairly fast kinetics for the adsorption of cadmium, copper and lead, permitting the use of high sample flow rates up to at least 3 mL·min-1 for the flow injection on micro-column preconcentration without the loss of the retention efficiency. The detection limits (3σ) were 0.03, 0.01 and 0.5 ng·mL-1 for Cd, Cu and Pb, respectively. The relative standard deviation under optimum condition is less than 2.9% (n = 10). The developed method was successfully applied to the determination of trace Cd, Cu and Pb in a variety of environmental and biological samples.

Ruthenium Catalyst Supported on Multi-Walled Carbon Nanotubes for CO Oxidation

This work proposes the synthesis of the 5%wt Ru on MWCNT catalyst and the influence of feed rate and testing variables for low-temperature oxidation affecting the CO2 yield. Morphology and incorporation of the nanoparticles in carbon nanotubes were investigated by specific surface area (BET method);thermogravimetric analyses (TGA);X-ray diffraction;Raman spectroscopy, transmission electron microscopy (TEM) and XPS. The conversions of CO and O2 were mostly 100% in groups C1 and C2 (temperature between 200 and 500°C with low WHSV). In order to assess the effect of mass on catalytic activity, condition C3 was tested at even lower temperatures. In the tested catalyst, high activity (100% CO and O2 conversion) was observed, keeping it active under reaction conditions, suggesting oxi-reduction of the RuO2 at surface without affecting the MWCNT but Lewis acid influencing the CO2 yield.

Mechanical Properties and Microstructure of Sulfur Aluminate Cement Composites Reinforced by Multi-walled Carbon Nanotubes

The effect of multi-walled carbon nanotubes（MWCNTs） on the mechanical properties and microstructure of sulfur aluminate cement（SAC） composites was investigated. The dispersed MWCNTs were added into SAC in various weight contents.The results of mechanical properties of the MWCNTs/SAC composites indicated that the addition of 0.08 wt% MWCNTs can improve the SAC compressive strength, flexural strength, and bend-press ratio by 15.54%, 52.38%, and 31.30% at maximum, respectively. The degree of SAC hydration and porosity and pore size distribution of the matrix were measured by X-ray diffraction（XRD）, thermal analysis（TG/DTG）, and mercury intrusion porosimetry（MIP）. Results show that the addition of MWCNTs in SAC composites can promote the hydration of SAC and the formation of C-S-H gel, reduce the porosity and refine the pore size distribution of the matrix. The microstructure was characterized by scanning electron microscopy（SEM） and energy dispersive spectroscopy（EDS）. It is found that the MWCNTs have been dispersed homogeneously between the hydration products of SAC paste and act as bridges and networks between cracks and voids, which prevents the development of the cracks and transfers the load.